1. Field of the Invention
This invention relates to a battery pack in which a battery pack core is insertion molded into a molded resin region. Specifically, this invention relates to a battery pack manufactured by temporarily holding the battery in a mold which forms the molded resin region, and by attaching the molded resin region to the battery by a process step which forms the molded resin region.
2. Description of the Related Art
Present battery packs are assembled by inserting a battery pack core, which is a battery and essential parts connected as a unit, into an external case formed of plastic. Since a battery pack of this configuration is assembled by attaching the battery pack core in a fixed position within the external case, its manufacture requires considerable effort. Accordingly, a battery pack which does not use an external case has been developed. This battery pack is manufactured by insertion of the battery pack core during formation of a molded resin region, which corresponds to the external case. In this configuration of battery pack, the battery pack core is fabricated by connecting essential components, such as connecting terminals, to the battery. The battery pack core is temporarily held in the mold cavity which forms the molded resin region. When molten synthetic resin is injected into the mold cavity, the injected resin adheres to the battery. Since the battery can be fixed relative to the molded resin region during molding, a battery pack manufactured in this way can efficiently be produced in quantity by omitting the external case. The molded resin region serves to anchor the battery, connecting terminals, and other components as a single unit as well as to form part of an external case for the battery pack. Consequently, since the battery pack core can form a solid unit when the molded resin region is formed, this battery pack configuration has the characteristic that it can be manufactured efficiently and inexpensively in quantity. This type of battery pack is cited, for example, in Japanese non-examined patent publication no. 315483/2000. As shown in FIG. 1, during formation of the molded resin region, which becomes the external case of the battery pack, the battery pack core 90 is inserted in the mold. Specifically, this battery pack is made by temporarily holding the battery pack core 90, which connects the battery 92, the circuit board 91, and other components comprising the battery pack, in the cavity 94 of the mold 93, injecting molten plastic into the mold cavity 94 to embed part of the inserted battery pack core 90 in the molded resin region, and finally by removing the unit from the mold after plastic solidification. In this battery pack, the battery pack core and molded resin region are attached as a single structure with no gaps allowing efficient manufacture in quantity.
In a battery pack manufactured with the structure described above, the molded resin region can be attached in a manner which closes off a battery safety valve opening, and the safety valve can thereby be protected by the molded resin region. When internal battery pressure exceeds a set pressure, the safety valve opens to exhaust gas, etc. to the exterior and prevent internal pressure from becoming abnormally high. A battery pack with a safety valve protected by molded resin region can prevent a user from inadvertently poking and damaging the safety valve opening with a needle-like object. However, during the manufacturing process for this type of battery pack when molten synthetic resin is injected to form the molded resin region which locally covers the safety valve opening, the pressure of the injected synthetic resin can damage the safety valve. To prevent this deleterious effect, the safety valve opening is covered with insulating material while the molded resin region is formed. The insulating material prevents resin injected into the mold cavity from entering the safety valve, and is used to prevent damage to the safety valve during molding.
However, it is difficult to reliably attach the molded resin region and insulating material in this type of battery pack. Since the molded resin region attaches to the battery with insulating material disposed between the two, the battery pack has the drawback that attachment strength between the battery and molded resin region is degraded. When attachment strength between the battery and molded resin region is degraded, the molded resin region can de-laminate from the battery during use rendering the battery pack unusable.
In addition, even though insulating material is attached to the safety valve opening, safety valve damage cannot reliably be prevented by insulating material which is easily deformed. This is because, as shown in FIG. 2, molten synthetic resin injected into the mold cavity for molded resin region formation can deform the insulating material 95 and damage the safety valve 96.
The present invention was developed with the objective of solving the problems described above. Thus it is a primary object of the present invention to provide a battery pack which reliably attaches the molded resin region and insulating material while preventing damage to the safety valve during molded resin region formation, and which does not result in molded resin region de-lamination.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.